Numerical simulation of influence of joint orientation on rock fragmentation process induced by a TBM cutter

A series of two dimension numerical modeling were performed using the discrete element method (DEM) to explore the effect of joint orientation on rock fragmentation process by a tunnel boring machine (TBM) rolling cutter. Numerical results show that the joint orientation can significantly influence the crack initiation and propagation, as well as the fragmentation pattern, and hence affect the penetration rate of the TBM. Two crack initiation and propagation modes are found to break the rock mass due to the variation of joint orientation. One is that the cracks initiate form the joint plane and propagate upwards to the free surface. The other is that the cracks initiate form the crushed zone and propagate downwards to the joint plane. The results also show that the stress field is deflected in different extent due to the occurrence of joint and the variation of the joint orientation. It makes the chipping angle increase with the increase of the angle between the tunnel axis and joint plane.